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We are going to track per-extent information, so it'll be necessary to
distinguish between inode infos and extent infos. Rename fscrypt_info
to fscrypt_inode_info, adjusting any lines that now exceed 80
characters.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
[ebiggers: rebased onto fscrypt tree, renamed fscrypt_get_info(),
adjusted two comments, and fixed some lines over 80 characters]
Link: https://lore.kernel.org/r/20231005025757.33521-1-ebiggers@kernel.org
Reviewed-by: Neal Gompa <neal@gompa.dev>
Signed-off-by: Eric Biggers <ebiggers@google.com>
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Until now, fscrypt has always used the filesystem block size as the
granularity of file contents encryption. Two scenarios have come up
where a sub-block granularity of contents encryption would be useful:
1. Inline crypto hardware that only supports a crypto data unit size
that is less than the filesystem block size.
2. Support for direct I/O at a granularity less than the filesystem
block size, for example at the block device's logical block size in
order to match the traditional direct I/O alignment requirement.
(1) first came up with older eMMC inline crypto hardware that only
supports a crypto data unit size of 512 bytes. That specific case
ultimately went away because all systems with that hardware continued
using out of tree code and never actually upgraded to the upstream
inline crypto framework. But, now it's coming back in a new way: some
current UFS controllers only support a data unit size of 4096 bytes, and
there is a proposal to increase the filesystem block size to 16K.
(2) was discussed as a "nice to have" feature, though not essential,
when support for direct I/O on encrypted files was being upstreamed.
Still, the fact that this feature has come up several times does suggest
it would be wise to have available. Therefore, this patch implements it
by using one of the reserved bytes in fscrypt_policy_v2 to allow users
to select a sub-block data unit size. Supported data unit sizes are
powers of 2 between 512 and the filesystem block size, inclusively.
Support is implemented for both the FS-layer and inline crypto cases.
This patch focuses on the basic support for sub-block data units. Some
things are out of scope for this patch but may be addressed later:
- Supporting sub-block data units in combination with
FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64, in most cases. Unfortunately this
combination usually causes data unit indices to exceed 32 bits, and
thus fscrypt_supported_policy() correctly disallows it. The users who
potentially need this combination are using f2fs. To support it, f2fs
would need to provide an option to slightly reduce its max file size.
- Supporting sub-block data units in combination with
FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32. This has the same problem
described above, but also it will need special code to make DUN
wraparound still happen on a FS block boundary.
- Supporting use case (2) mentioned above. The encrypted direct I/O
code will need to stop requiring and assuming FS block alignment.
This won't be hard, but it belongs in a separate patch.
- Supporting this feature on filesystems other than ext4 and f2fs.
(Filesystems declare support for it via their fscrypt_operations.)
On UBIFS, sub-block data units don't make sense because UBIFS encrypts
variable-length blocks as a result of compression. CephFS could
support it, but a bit more work would be needed to make the
fscrypt_*_block_inplace functions play nicely with sub-block data
units. I don't think there's a use case for this on CephFS anyway.
Link: https://lore.kernel.org/r/20230925055451.59499-6-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
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Now that fs/crypto/ computes the filesystem's lblk_bits from its maximum
file size, it is no longer necessary for filesystems to provide
lblk_bits via fscrypt_operations::get_ino_and_lblk_bits.
It is still necessary for fs/crypto/ to retrieve ino_bits from the
filesystem. However, this is used only to decide whether inode numbers
fit in 32 bits. Also, ino_bits is static for all relevant filesystems,
i.e. it doesn't depend on the filesystem instance.
Therefore, in the interest of keeping things as simple as possible,
replace 'get_ino_and_lblk_bits' with a flag 'has_32bit_inodes'. This
can always be changed back to a function if a filesystem needs it to be
dynamic, but for now a static flag is all that's needed.
Link: https://lore.kernel.org/r/20230925055451.59499-5-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
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For a given filesystem, the number of bits used by the maximum file
logical block number is computable from the maximum file size and the
block size. These values are always present in struct super_block.
Therefore, compute it this way instead of using the value from
fscrypt_operations::get_ino_and_lblk_bits. Since filesystems always
have to set the super_block fields anyway, this avoids having to provide
this information redundantly via fscrypt_operations.
This change is in preparation for adding support for sub-block data
units. For that, the value that is needed will become "the maximum file
data unit index". A hardcoded value won't suffice for that; it will
need to be computed anyway.
Link: https://lore.kernel.org/r/20230925055451.59499-4-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
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As per Linus's suggestion
(https://lore.kernel.org/r/CAHk-=whefxRGyNGzCzG6BVeM=5vnvgb-XhSeFJVxJyAxAF8XRA@mail.gmail.com),
use WARN_ON_ONCE instead of WARN_ON. This barely adds any extra
overhead, and it makes it so that if any of these ever becomes reachable
(they shouldn't, but that's the point), the logs can't be flooded.
Link: https://lore.kernel.org/r/20230320233943.73600-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
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Pull fscrypt updates from Eric Biggers:
"Simplify the implementation of the test_dummy_encryption mount option
by adding the 'test dummy key' on-demand"
* tag 'fscrypt-for-linus' of git://git.kernel.org/pub/scm/fs/fscrypt/linux:
fscrypt: clean up fscrypt_add_test_dummy_key()
fs/super.c: stop calling fscrypt_destroy_keyring() from __put_super()
f2fs: stop calling fscrypt_add_test_dummy_key()
ext4: stop calling fscrypt_add_test_dummy_key()
fscrypt: add the test dummy encryption key on-demand
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When the key for an inode is not found but the inode is using the
test_dummy_encryption policy, automatically add the
test_dummy_encryption key to the filesystem keyring. This eliminates
the need for all the individual filesystems to do this at mount time,
which is a bit tricky to clean up from on failure.
Note: this covers the call to fscrypt_find_master_key() from inode key
setup, but not from the fscrypt ioctls. So, this isn't *exactly* the
same as the key being present from the very beginning. I think we can
tolerate that, though, since the inode key setup caller is the only one
that actually matters in the context of test_dummy_encryption.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20230208062107.199831-2-ebiggers@kernel.org
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Convert to struct mnt_idmap.
Last cycle we merged the necessary infrastructure in
256c8aed2b42 ("fs: introduce dedicated idmap type for mounts").
This is just the conversion to struct mnt_idmap.
Currently we still pass around the plain namespace that was attached to a
mount. This is in general pretty convenient but it makes it easy to
conflate namespaces that are relevant on the filesystem with namespaces
that are relevent on the mount level. Especially for non-vfs developers
without detailed knowledge in this area this can be a potential source for
bugs.
Once the conversion to struct mnt_idmap is done all helpers down to the
really low-level helpers will take a struct mnt_idmap argument instead of
two namespace arguments. This way it becomes impossible to conflate the two
eliminating the possibility of any bugs. All of the vfs and all filesystems
only operate on struct mnt_idmap.
Acked-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
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Add support for XTS and CTS mode variant of SM4 algorithm. The former is
used to encrypt file contents, while the latter (SM4-CTS-CBC) is used to
encrypt filenames.
SM4 is a symmetric algorithm widely used in China, and is even mandatory
algorithm in some special scenarios. We need to provide these users with
the ability to encrypt files or disks using SM4-XTS.
Signed-off-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20221201125819.36932-3-tianjia.zhang@linux.alibaba.com
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Make it clear that nothing new should be added to this function.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20221125192047.18916-1-ebiggers@kernel.org
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The approach of fs/crypto/ internally managing the fscrypt_master_key
structs as the payloads of "struct key" objects contained in a
"struct key" keyring has outlived its usefulness. The original idea was
to simplify the code by reusing code from the keyrings subsystem.
However, several issues have arisen that can't easily be resolved:
- When a master key struct is destroyed, blk_crypto_evict_key() must be
called on any per-mode keys embedded in it. (This started being the
case when inline encryption support was added.) Yet, the keyrings
subsystem can arbitrarily delay the destruction of keys, even past the
time the filesystem was unmounted. Therefore, currently there is no
easy way to call blk_crypto_evict_key() when a master key is
destroyed. Currently, this is worked around by holding an extra
reference to the filesystem's request_queue(s). But it was overlooked
that the request_queue reference is *not* guaranteed to pin the
corresponding blk_crypto_profile too; for device-mapper devices that
support inline crypto, it doesn't. This can cause a use-after-free.
- When the last inode that was using an incompletely-removed master key
is evicted, the master key removal is completed by removing the key
struct from the keyring. Currently this is done via key_invalidate().
Yet, key_invalidate() takes the key semaphore. This can deadlock when
called from the shrinker, since in fscrypt_ioctl_add_key(), memory is
allocated with GFP_KERNEL under the same semaphore.
- More generally, the fact that the keyrings subsystem can arbitrarily
delay the destruction of keys (via garbage collection delay, or via
random processes getting temporary key references) is undesirable, as
it means we can't strictly guarantee that all secrets are ever wiped.
- Doing the master key lookups via the keyrings subsystem results in the
key_permission LSM hook being called. fscrypt doesn't want this, as
all access control for encrypted files is designed to happen via the
files themselves, like any other files. The workaround which SELinux
users are using is to change their SELinux policy to grant key search
access to all domains. This works, but it is an odd extra step that
shouldn't really have to be done.
The fix for all these issues is to change the implementation to what I
should have done originally: don't use the keyrings subsystem to keep
track of the filesystem's fscrypt_master_key structs. Instead, just
store them in a regular kernel data structure, and rework the reference
counting, locking, and lifetime accordingly. Retain support for
RCU-mode key lookups by using a hash table. Replace fscrypt_sb_free()
with fscrypt_sb_delete(), which releases the keys synchronously and runs
a bit earlier during unmount, so that block devices are still available.
A side effect of this patch is that neither the master keys themselves
nor the filesystem keyrings will be listed in /proc/keys anymore.
("Master key users" and the master key users keyrings will still be
listed.) However, this was mostly an implementation detail, and it was
intended just for debugging purposes. I don't know of anyone using it.
This patch does *not* change how "master key users" (->mk_users) works;
that still uses the keyrings subsystem. That is still needed for key
quotas, and changing that isn't necessary to solve the issues listed
above. If we decide to change that too, it would be a separate patch.
I've marked this as fixing the original commit that added the fscrypt
keyring, but as noted above the most important issue that this patch
fixes wasn't introduced until the addition of inline encryption support.
Fixes: 22d94f493bfb ("fscrypt: add FS_IOC_ADD_ENCRYPTION_KEY ioctl")
Signed-off-by: Eric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20220901193208.138056-2-ebiggers@kernel.org
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Now that all its callers have been converted to
fscrypt_parse_test_dummy_encryption() and fscrypt_add_test_dummy_key()
instead, fscrypt_set_test_dummy_encryption() can be removed.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20220513231605.175121-6-ebiggers@kernel.org
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Pull ceph updates from Ilya Dryomov:
"We have a good pile of various fixes and cleanups from Xiubo, Jeff,
Luis and others, almost exclusively in the filesystem.
Several patches touch files outside of our normal purview to set the
stage for bringing in Jeff's long awaited ceph+fscrypt series in the
near future. All of them have appropriate acks and sat in linux-next
for a while"
* tag 'ceph-for-5.20-rc1' of https://github.com/ceph/ceph-client: (27 commits)
libceph: clean up ceph_osdc_start_request prototype
libceph: fix ceph_pagelist_reserve() comment typo
ceph: remove useless check for the folio
ceph: don't truncate file in atomic_open
ceph: make f_bsize always equal to f_frsize
ceph: flush the dirty caps immediatelly when quota is approaching
libceph: print fsid and epoch with osd id
libceph: check pointer before assigned to "c->rules[]"
ceph: don't get the inline data for new creating files
ceph: update the auth cap when the async create req is forwarded
ceph: make change_auth_cap_ses a global symbol
ceph: fix incorrect old_size length in ceph_mds_request_args
ceph: switch back to testing for NULL folio->private in ceph_dirty_folio
ceph: call netfs_subreq_terminated with was_async == false
ceph: convert to generic_file_llseek
ceph: fix the incorrect comment for the ceph_mds_caps struct
ceph: don't leak snap_rwsem in handle_cap_grant
ceph: prevent a client from exceeding the MDS maximum xattr size
ceph: choose auth MDS for getxattr with the Xs caps
ceph: add session already open notify support
...
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Most filesystems just call fscrypt_set_context on new inodes, which
usually causes a setxattr. That's a bit late for ceph, which can send
along a full set of attributes with the create request.
Doing so allows it to avoid race windows that where the new inode could
be seen by other clients without the crypto context attached. It also
avoids the separate round trip to the server.
Refactor the fscrypt code a bit to allow us to create a new crypto
context, attach it to the inode, and write it to the buffer, but without
calling set_context on it. ceph can later use this to marshal the
context into the attributes we send along with the create request.
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Xiubo Li <xiubli@redhat.com>
Acked-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
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HCTR2 is a tweakable, length-preserving encryption mode that is intended
for use on CPUs with dedicated crypto instructions. HCTR2 has the
property that a bitflip in the plaintext changes the entire ciphertext.
This property fixes a known weakness with filename encryption: when two
filenames in the same directory share a prefix of >= 16 bytes, with
AES-CTS-CBC their encrypted filenames share a common substring, leaking
information. HCTR2 does not have this problem.
More information on HCTR2 can be found here: "Length-preserving
encryption with HCTR2": https://eprint.iacr.org/2021/1441.pdf
Signed-off-by: Nathan Huckleberry <nhuck@google.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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Unfortunately the design of fscrypt_set_test_dummy_encryption() doesn't
work properly for the new mount API, as it combines too many steps into
one function:
- Parse the argument to test_dummy_encryption
- Check the setting against the filesystem instance
- Apply the setting to the filesystem instance
The new mount API has split these into separate steps. ext4 partially
worked around this by duplicating some of the logic, but it still had
some bugs. To address this, add some new helper functions that split up
the steps of fscrypt_set_test_dummy_encryption():
- fscrypt_parse_test_dummy_encryption()
- fscrypt_dummy_policies_equal()
- fscrypt_add_test_dummy_key()
While we're add it, also add a function fscrypt_is_dummy_policy_set()
which will be useful to avoid some #ifdef's.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20220501050857.538984-5-ebiggers@kernel.org
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Factor out a function that builds the fscrypt_key_specifier for an
fscrypt_policy. Before this was only needed when finding the key for a
file, but now it will also be needed for test_dummy_encryption support.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20220501050857.538984-4-ebiggers@kernel.org
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The inode_owner_or_capable() helper determines whether the caller is the
owner of the inode or is capable with respect to that inode. Allow it to
handle idmapped mounts. If the inode is accessed through an idmapped
mount it according to the mount's user namespace. Afterwards the checks
are identical to non-idmapped mounts. If the initial user namespace is
passed nothing changes so non-idmapped mounts will see identical
behavior as before.
Similarly, allow the inode_init_owner() helper to handle idmapped
mounts. It initializes a new inode on idmapped mounts by mapping the
fsuid and fsgid of the caller from the mount's user namespace. If the
initial user namespace is passed nothing changes so non-idmapped mounts
will see identical behavior as before.
Link: https://lore.kernel.org/r/20210121131959.646623-7-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: James Morris <jamorris@linux.microsoft.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
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Currently it's impossible to delete files that use an unsupported
encryption policy, as the kernel will just return an error when
performing any operation on the top-level encrypted directory, even just
a path lookup into the directory or opening the directory for readdir.
More specifically, this occurs in any of the following cases:
- The encryption context has an unrecognized version number. Current
kernels know about v1 and v2, but there could be more versions in the
future.
- The encryption context has unrecognized encryption modes
(FSCRYPT_MODE_*) or flags (FSCRYPT_POLICY_FLAG_*), an unrecognized
combination of modes, or reserved bits set.
- The encryption key has been added and the encryption modes are
recognized but aren't available in the crypto API -- for example, a
directory is encrypted with FSCRYPT_MODE_ADIANTUM but the kernel
doesn't have CONFIG_CRYPTO_ADIANTUM enabled.
It's desirable to return errors for most operations on files that use an
unsupported encryption policy, but the current behavior is too strict.
We need to allow enough to delete files, so that people can't be stuck
with undeletable files when downgrading kernel versions. That includes
allowing directories to be listed and allowing dentries to be looked up.
Fix this by modifying the key setup logic to treat an unsupported
encryption policy in the same way as "key unavailable" in the cases that
are required for a recursive delete to work: preparing for a readdir or
a dentry lookup, revalidating a dentry, or checking whether an inode has
the same encryption policy as its parent directory.
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Link: https://lore.kernel.org/r/20201203022041.230976-10-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
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There isn't really any valid reason to use __FSCRYPT_MODE_MAX or
FSCRYPT_POLICY_FLAGS_VALID in a userspace program. These constants are
only meant to be used by the kernel internally, and they are defined in
the UAPI header next to the mode numbers and flags only so that kernel
developers don't forget to update them when adding new modes or flags.
In https://lkml.kernel.org/r/20201005074133.1958633-2-satyat@google.com
there was an example of someone wanting to use __FSCRYPT_MODE_MAX in a
user program, and it was wrong because the program would have broken if
__FSCRYPT_MODE_MAX were ever increased. So having this definition
available is harmful. FSCRYPT_POLICY_FLAGS_VALID has the same problem.
So, remove these definitions from the UAPI header. Replace
FSCRYPT_POLICY_FLAGS_VALID with just listing the valid flags explicitly
in the one kernel function that needs it. Move __FSCRYPT_MODE_MAX to
fscrypt_private.h, remove the double underscores (which were only
present to discourage use by userspace), and add a BUILD_BUG_ON() and
comments to (hopefully) ensure it is kept in sync.
Keep the old name FS_POLICY_FLAGS_VALID, since it's been around for
longer and there's a greater chance that removing it would break source
compatibility with some program. Indeed, mtd-utils is using it in
an #ifdef, and removing it would introduce compiler warnings (about
FS_POLICY_FLAGS_PAD_* being redefined) into the mtd-utils build.
However, reduce its value to 0x07 so that it only includes the flags
with old names (the ones present before Linux 5.4), and try to make it
clear that it's now "frozen" and no new flags should be added to it.
Fixes: 2336d0deb2d4 ("fscrypt: use FSCRYPT_ prefix for uapi constants")
Cc: <stable@vger.kernel.org> # v5.4+
Link: https://lore.kernel.org/r/20201024005132.495952-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
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fscrypt_set_test_dummy_encryption() requires that the optional argument
to the test_dummy_encryption mount option be specified as a substring_t.
That doesn't work well with filesystems that use the new mount API,
since the new way of parsing mount options doesn't use substring_t.
Make it take the argument as a 'const char *' instead.
Instead of moving the match_strdup() into the callers in ext4 and f2fs,
make them just use arg->from directly. Since the pattern is
"test_dummy_encryption=%s", the argument will be null-terminated.
Acked-by: Jeff Layton <jlayton@kernel.org>
Link: https://lore.kernel.org/r/20200917041136.178600-14-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
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The behavior of the test_dummy_encryption mount option is that when a
new file (or directory or symlink) is created in an unencrypted
directory, it's automatically encrypted using a dummy encryption policy.
That's it; in particular, the encryption (or lack thereof) of existing
files (or directories or symlinks) doesn't change.
Unfortunately the implementation of test_dummy_encryption is a bit weird
and confusing. When test_dummy_encryption is enabled and a file is
being created in an unencrypted directory, we set up an encryption key
(->i_crypt_info) for the directory. This isn't actually used to do any
encryption, however, since the directory is still unencrypted! Instead,
->i_crypt_info is only used for inheriting the encryption policy.
One consequence of this is that the filesystem ends up providing a
"dummy context" (policy + nonce) instead of a "dummy policy". In
commit ed318a6cc0b6 ("fscrypt: support test_dummy_encryption=v2"), I
mistakenly thought this was required. However, actually the nonce only
ends up being used to derive a key that is never used.
Another consequence of this implementation is that it allows for
'inode->i_crypt_info != NULL && !IS_ENCRYPTED(inode)', which is an edge
case that can be forgotten about. For example, currently
FS_IOC_GET_ENCRYPTION_POLICY on an unencrypted directory may return the
dummy encryption policy when the filesystem is mounted with
test_dummy_encryption. That seems like the wrong thing to do, since
again, the directory itself is not actually encrypted.
Therefore, switch to a more logical and maintainable implementation
where the dummy encryption policy inheritance is done without setting up
keys for unencrypted directories. This involves:
- Adding a function fscrypt_policy_to_inherit() which returns the
encryption policy to inherit from a directory. This can be a real
policy, a dummy policy, or no policy.
- Replacing struct fscrypt_dummy_context, ->get_dummy_context(), etc.
with struct fscrypt_dummy_policy, ->get_dummy_policy(), etc.
- Making fscrypt_fname_encrypted_size() take an fscrypt_policy instead
of an inode.
Acked-by: Jaegeuk Kim <jaegeuk@kernel.org>
Acked-by: Jeff Layton <jlayton@kernel.org>
Link: https://lore.kernel.org/r/20200917041136.178600-13-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
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Now that all filesystems have been converted to use
fscrypt_prepare_new_inode() and fscrypt_set_context(),
fscrypt_inherit_context() is no longer used. Remove it.
Acked-by: Jeff Layton <jlayton@kernel.org>
Link: https://lore.kernel.org/r/20200917041136.178600-8-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
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fscrypt_get_encryption_info() is intended to be GFP_NOFS-safe. But
actually it isn't, since it uses functions like crypto_alloc_skcipher()
which aren't GFP_NOFS-safe, even when called under memalloc_nofs_save().
Therefore it can deadlock when called from a context that needs
GFP_NOFS, e.g. during an ext4 transaction or between f2fs_lock_op() and
f2fs_unlock_op(). This happens when creating a new encrypted file.
We can't fix this by just not setting up the key for new inodes right
away, since new symlinks need their key to encrypt the symlink target.
So we need to set up the new inode's key before starting the
transaction. But just calling fscrypt_get_encryption_info() earlier
doesn't work, since it assumes the encryption context is already set,
and the encryption context can't be set until the transaction.
The recently proposed fscrypt support for the ceph filesystem
(https://lkml.kernel.org/linux-fscrypt/20200821182813.52570-1-jlayton@kernel.org/T/#u)
will have this same ordering problem too, since ceph will need to
encrypt new symlinks before setting their encryption context.
Finally, f2fs can deadlock when the filesystem is mounted with
'-o test_dummy_encryption' and a new file is created in an existing
unencrypted directory. Similarly, this is caused by holding too many
locks when calling fscrypt_get_encryption_info().
To solve all these problems, add new helper functions:
- fscrypt_prepare_new_inode() sets up a new inode's encryption key
(fscrypt_info), using the parent directory's encryption policy and a
new random nonce. It neither reads nor writes the encryption context.
- fscrypt_set_context() persists the encryption context of a new inode,
using the information from the fscrypt_info already in memory. This
replaces fscrypt_inherit_context().
Temporarily keep fscrypt_inherit_context() around until all filesystems
have been converted to use fscrypt_set_context().
Acked-by: Jeff Layton <jlayton@kernel.org>
Link: https://lore.kernel.org/r/20200917041136.178600-2-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
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When an encryption policy has the IV_INO_LBLK_32 flag set, the IV
generation method involves hashing the inode number. This is different
from fscrypt's other IV generation methods, where the inode number is
either not used at all or is included directly in the IVs.
Therefore, in principle IV_INO_LBLK_32 can work with any length inode
number. However, currently fscrypt gets the inode number from
inode::i_ino, which is 'unsigned long'. So currently the implementation
limit is actually 32 bits (like IV_INO_LBLK_64), since longer inode
numbers will have been truncated by the VFS on 32-bit platforms.
Fix fscrypt_supported_v2_policy() to enforce the correct limit.
This doesn't actually matter currently, since only ext4 and f2fs support
IV_INO_LBLK_32, and they both only support 32-bit inode numbers. But we
might as well fix it in case it matters in the future.
Ideally inode::i_ino would instead be made 64-bit, but for now it's not
needed. (Note, this limit does *not* prevent filesystems with 64-bit
inode numbers from adding fscrypt support, since IV_INO_LBLK_* support
is optional and is useful only on certain hardware.)
Fixes: e3b1078bedd3 ("fscrypt: add support for IV_INO_LBLK_32 policies")
Reported-by: Jeff Layton <jlayton@kernel.org>
Link: https://lore.kernel.org/r/20200824203841.1707847-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
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Normally smp_store_release() or cmpxchg_release() is paired with
smp_load_acquire(). Sometimes smp_load_acquire() can be replaced with
the more lightweight READ_ONCE(). However, for this to be safe, all the
published memory must only be accessed in a way that involves the
pointer itself. This may not be the case if allocating the object also
involves initializing a static or global variable, for example.
fscrypt_info includes various sub-objects which are internal to and are
allocated by other kernel subsystems such as keyrings and crypto. So by
using READ_ONCE() for ->i_crypt_info, we're relying on internal
implementation details of these other kernel subsystems.
Remove this fragile assumption by using smp_load_acquire() instead.
(Note: I haven't seen any real-world problems here. This change is just
fixing the code to be guaranteed correct and less fragile.)
Fixes: e37a784d8b6a ("fscrypt: use READ_ONCE() to access ->i_crypt_info")
Link: https://lore.kernel.org/r/20200721225920.114347-5-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
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IV_INO_LBLK_* exist only because of hardware limitations, and currently
the only known use case for them involves AES-256-XTS. Therefore, for
now only allow them in combination with AES-256-XTS. This way we don't
have to worry about them being combined with other encryption modes.
(To be clear, combining IV_INO_LBLK_* with other encryption modes
*should* work just fine. It's just not being tested, so we can't be
100% sure it works. So with no known use case, it's best to disallow it
for now, just like we don't allow other weird combinations like
AES-256-XTS contents encryption with Adiantum filenames encryption.)
This can be relaxed later if a use case for other combinations arises.
Fixes: b103fb7653ff ("fscrypt: add support for IV_INO_LBLK_64 policies")
Fixes: e3b1078bedd3 ("fscrypt: add support for IV_INO_LBLK_32 policies")
Link: https://lore.kernel.org/r/20200721181012.39308-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
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The name "FS_KEY_DERIVATION_NONCE_SIZE" is a bit outdated since due to
the addition of FSCRYPT_POLICY_FLAG_DIRECT_KEY, the file nonce may now
be used as a tweak instead of for key derivation. Also, we're now
prefixing the fscrypt constants with "FSCRYPT_" instead of "FS_".
Therefore, rename this constant to FSCRYPT_FILE_NONCE_SIZE.
Link: https://lore.kernel.org/r/20200708215722.147154-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
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The eMMC inline crypto standard will only specify 32 DUN bits (a.k.a. IV
bits), unlike UFS's 64. IV_INO_LBLK_64 is therefore not applicable, but
an encryption format which uses one key per policy and permits the
moving of encrypted file contents (as f2fs's garbage collector requires)
is still desirable.
To support such hardware, add a new encryption format IV_INO_LBLK_32
that makes the best use of the 32 bits: the IV is set to
'SipHash-2-4(inode_number) + file_logical_block_number mod 2^32', where
the SipHash key is derived from the fscrypt master key. We hash only
the inode number and not also the block number, because we need to
maintain contiguity of DUNs to merge bios.
Unlike with IV_INO_LBLK_64, with this format IV reuse is possible; this
is unavoidable given the size of the DUN. This means this format should
only be used where the requirements of the first paragraph apply.
However, the hash spreads out the IVs in the whole usable range, and the
use of a keyed hash makes it difficult for an attacker to determine
which files use which IVs.
Besides the above differences, this flag works like IV_INO_LBLK_64 in
that on ext4 it is only allowed if the stable_inodes feature has been
enabled to prevent inode numbers and the filesystem UUID from changing.
Link: https://lore.kernel.org/r/20200515204141.251098-1-ebiggers@kernel.org
Reviewed-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Paul Crowley <paulcrowley@google.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
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Since v1 encryption policies are deprecated, make test_dummy_encryption
test v2 policies by default.
Note that this causes ext4/023 and ext4/028 to start failing due to
known bugs in those tests (see previous commit).
Link: https://lore.kernel.org/r/20200512233251.118314-5-ebiggers@kernel.org
Reviewed-by: Jaegeuk Kim <jaegeuk@kernel.org>
Reviewed-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Eric Biggers <ebiggers@google.com>
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v1 encryption policies are deprecated in favor of v2, and some new
features (e.g. encryption+casefolding) are only being added for v2.
Therefore, the "test_dummy_encryption" mount option (which is used for
encryption I/O testing with xfstests) needs to support v2 policies.
To do this, extend its syntax to be "test_dummy_encryption=v1" or
"test_dummy_encryption=v2". The existing "test_dummy_encryption" (no
argument) also continues to be accepted, to specify the default setting
-- currently v1, but the next patch changes it to v2.
To cleanly support both v1 and v2 while also making it easy to support
specifying other encryption settings in the future (say, accepting
"$contents_mode:$filenames_mode:v2"), make ext4 and f2fs maintain a
pointer to the dummy fscrypt_context rather than using mount flags.
To avoid concurrency issues, don't allow test_dummy_encryption to be set
or changed during a remount. (The former restriction is new, but
xfstests doesn't run into it, so no one should notice.)
Tested with 'gce-xfstests -c {ext4,f2fs}/encrypt -g auto'. On ext4,
there are two regressions, both of which are test bugs: ext4/023 and
ext4/028 fail because they set an xattr and expect it to be stored
inline, but the increase in size of the fscrypt_context from
24 to 40 bytes causes this xattr to be spilled into an external block.
Link: https://lore.kernel.org/r/20200512233251.118314-4-ebiggers@kernel.org
Acked-by: Jaegeuk Kim <jaegeuk@kernel.org>
Reviewed-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Eric Biggers <ebiggers@google.com>
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Fix all kerneldoc warnings in fs/crypto/ and include/linux/fscrypt.h.
Most of these were due to missing documentation for function parameters.
Detected with:
scripts/kernel-doc -v -none fs/crypto/*.{c,h} include/linux/fscrypt.h
This cleanup makes it possible to check new patches for kerneldoc
warnings without having to filter out all the existing ones.
For consistency, also adjust some function "brief descriptions" to
include the parentheses and to wrap at 80 characters. (The latter
matches the checkpatch expectation.)
Link: https://lore.kernel.org/r/20200511191358.53096-2-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
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Add an ioctl FS_IOC_GET_ENCRYPTION_NONCE which retrieves the nonce from
an encrypted file or directory. The nonce is the 16-byte random value
stored in the inode's encryption xattr. It is normally used together
with the master key to derive the inode's actual encryption key.
The nonces are needed by automated tests that verify the correctness of
the ciphertext on-disk. Except for the IV_INO_LBLK_64 case, there's no
way to replicate a file's ciphertext without knowing that file's nonce.
The nonces aren't secret, and the existing ciphertext verification tests
in xfstests retrieve them from disk using debugfs or dump.f2fs. But in
environments that lack these debugging tools, getting the nonces by
manually parsing the filesystem structure would be very hard.
To make this important type of testing much easier, let's just add an
ioctl that retrieves the nonce.
Link: https://lore.kernel.org/r/20200314205052.93294-2-ebiggers@kernel.org
Reviewed-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Eric Biggers <ebiggers@google.com>
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Casefolded encrypted directories will use a new dirhash method that
requires a secret key. If the directory uses a v2 encryption policy,
it's easy to derive this key from the master key using HKDF. However,
v1 encryption policies don't provide a way to derive additional keys.
Therefore, don't allow casefolding on directories that use a v1 policy.
Specifically, make it so that trying to enable casefolding on a
directory that has a v1 policy fails, trying to set a v1 policy on a
casefolded directory fails, and trying to open a casefolded directory
that has a v1 policy (if one somehow exists on-disk) fails.
Signed-off-by: Daniel Rosenberg <drosen@google.com>
[EB: improved commit message, updated fscrypt.rst, and other cleanups]
Link: https://lore.kernel.org/r/20200120223201.241390-2-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
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fscrypt_valid_enc_modes() is only used by policy.c, so move it to there.
Also adjust the order of the checks to be more natural, matching the
numerical order of the constants and also keeping AES-256 (the
recommended default) first in the list.
No change in behavior.
Link: https://lore.kernel.org/r/20191209211829.239800-4-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
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FSCRYPT_POLICY_FLAG_DIRECT_KEY is currently only allowed with Adiantum
encryption. But FS_IOC_SET_ENCRYPTION_POLICY allowed it in combination
with other encryption modes, and an error wasn't reported until later
when the encrypted directory was actually used.
Fix it to report the error earlier by validating the correct use of the
DIRECT_KEY flag in fscrypt_supported_policy(), similar to how we
validate the IV_INO_LBLK_64 flag.
Link: https://lore.kernel.org/r/20191209211829.239800-3-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
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Make fscrypt_supported_policy() call new functions
fscrypt_supported_v1_policy() and fscrypt_supported_v2_policy(), to
reduce the indentation level and make the code easier to read.
Also adjust the function comment to mention that whether the encryption
policy is supported can also depend on the inode.
No change in behavior.
Link: https://lore.kernel.org/r/20191209211829.239800-2-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
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Inline encryption hardware compliant with the UFS v2.1 standard or with
the upcoming version of the eMMC standard has the following properties:
(1) Per I/O request, the encryption key is specified by a previously
loaded keyslot. There might be only a small number of keyslots.
(2) Per I/O request, the starting IV is specified by a 64-bit "data unit
number" (DUN). IV bits 64-127 are assumed to be 0. The hardware
automatically increments the DUN for each "data unit" of
configurable size in the request, e.g. for each filesystem block.
Property (1) makes it inefficient to use the traditional fscrypt
per-file keys. Property (2) precludes the use of the existing
DIRECT_KEY fscrypt policy flag, which needs at least 192 IV bits.
Therefore, add a new fscrypt policy flag IV_INO_LBLK_64 which causes the
encryption to modified as follows:
- The encryption keys are derived from the master key, encryption mode
number, and filesystem UUID.
- The IVs are chosen as (inode_number << 32) | file_logical_block_num.
For filenames encryption, file_logical_block_num is 0.
Since the file nonces aren't used in the key derivation, many files may
share the same encryption key. This is much more efficient on the
target hardware. Including the inode number in the IVs and mixing the
filesystem UUID into the keys ensures that data in different files is
nevertheless still encrypted differently.
Additionally, limiting the inode and block numbers to 32 bits and
placing the block number in the low bits maintains compatibility with
the 64-bit DUN convention (property (2) above).
Since this scheme assumes that inode numbers are stable (which may
preclude filesystem shrinking) and that inode and file logical block
numbers are at most 32-bit, IV_INO_LBLK_64 will only be allowed on
filesystems that meet these constraints. These are acceptable
limitations for the cases where this format would actually be used.
Note that IV_INO_LBLK_64 is an on-disk format, not an implementation.
This patch just adds support for it using the existing filesystem layer
encryption. A later patch will add support for inline encryption.
Reviewed-by: Paul Crowley <paulcrowley@google.com>
Co-developed-by: Satya Tangirala <satyat@google.com>
Signed-off-by: Satya Tangirala <satyat@google.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
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By looking up the master keys in a filesystem-level keyring rather than
in the calling processes' key hierarchy, it becomes possible for a user
to set an encryption policy which refers to some key they don't actually
know, then encrypt their files using that key. Cryptographically this
isn't much of a problem, but the semantics of this would be a bit weird.
Thus, enforce that a v2 encryption policy can only be set if the user
has previously added the key, or has capable(CAP_FOWNER).
We tolerate that this problem will continue to exist for v1 encryption
policies, however; there is |
